The present invention relates generally to the field of methods and apparatuses for testing characteristics of elastomeric weatherstrips. In particular, the invention is concerned with a method and apparatus for testing seal load, relaxation rate, and recovery rate of extruded elastomeric weatherstrips.
Extruded elastomeric weatherstrips are commonly used to provide sealing between the edges of openings of motor vehicle bodies and closure elements for those openings. These weatherstrips provide protection from air, dust, and water passing through door, trunk, and window seals. To perform effectively, the weatherstrips must be manufactured to given specifications.
An elastomeric weatherstrip typically includes a first section for securing the weatherstrip to an edge of an opening in a motor vehicle body or a closure element for that opening and a second section, such as a wing, or bulb for providing sealing therebetween. An important characteristic of an elastomeric weatherstrip is the amount of force that is required to deflect the wing or bulb of the weatherstrip a selected distance. The selected distance typically corresponds to the distance that the wing or bulb will be deflected when the weatherstrip is in use. The amount of force required to so deflect the weatherstrip is typically referred to as "seal load." Ideally, a weatherstrip should have a seal load which is low enough to prevent the need for excessive force to close a window, trunk, door, or the like, while high enough to maintain effective sealing in the sealed seam.
Another important characteristic of an elastomeric weatherstrip is stress relaxation, which is the decrease in stress over time at a constant deformation. Stress relaxation is important in engineering applications because it can cause the applied seal force to become unacceptably low during operation. The force generated by a deflected weatherstrip having a high stress relaxation will decrease quickly and will result in inferior sealing in the seam in which the thus relaxed weatherstrip is positioned.
A third characteristic of an elastomeric weatherstrip is seal recovery. Seal recovery refers to the rate at which a deflected portion of a weatherstrip returns to its predeflection condition after the deflecting force has been removed. For purposes of providing effective sealing, a high seal recovery rate is desirable.
There is presently in the industry a felt need for economical and reliable measurement of the above-discussed characteristics of an extruded elastomeric weatherstrip. As a result, weatherstrips at times are manufactured without these characteristics having been monitored either adequately or at all. Accordingly, while relatively minor mechanical adjustments to the manufacturing process can improve weatherstrip quality, if that quality is not monitored the adjustments are not made and inferior weatherstrips are produced.
It is, therefore, an object of the present invention to provide an apparatus for economically and reliably measuring the above-discussed characteristics of an extruded elastomeric weatherstrip. It is a further object of the present invention to provide a method for measuring these characteristics which provides accurate data and is simple to implement. Yet another object of the present invention is to enable a superior weatherstrip to be manufactured by affording manufacturers the ability to easily monitor important characteristics of weatherstrips.